1. Field of the Invention
This invention relates broadly to temperature measuring apparatus and more particularly to optical field scanning pyrometer systems.
2. Description of the Prior Art
There has been a long standing need to better control the finishing temperature of hot steel products rolled in many bar and sheet mills. Without accurate temperature control problems frequently arise with duplex grain and secondary scale growth which in themselves lead to subsequent problems connected with forming and pickling. Sometimes solutions to these and other problems require computer analysis involving temperature data to effect real-time process control.
Conventional pyrometers require continuous sighting on a hot target, and the target image fill the entire field, in order to provide a reasonably accurate temperature measurement of the target. Ordinarily the target must be stationary, but if movable must have sufficient area and uniformity of radiation characteristics to effictively fill the entire field at all times. In addition, convention pyrometer response is rather slow to rapid changes in temperature.
Thus, it will be appreciated that conventional pyrometers impose severe limitations on accurately and rapidly measuring the temperature, for example, of a small diameter hot bar (the target) moving longitudinally very rapidly through a bar mill while constantly vibrating in a lateral orbit defining a large image field, and in addition, experiencing rapid increases and/or decreases in bar temperature. Even modified pyrometers incorporating a peak-picker circuit with adjustable decay rates are not very satisfactory for such installations. Disadvantages with this approach is that the modified pyrometer is inherently slow and cannot be used, for example, in computer analysis. In addition, it can only follow temperature changes in one preset direction, either up or down, but not in both directions. Furthermore, it lacks scanning features to locate hot objects in an adjustable width field.